1. Field of the Invention
This invention relates to a composition for ultra-fine pattern formation of a resist for transistors, integrated circuits (IC), large scale integrated circuits (LSI) or the like in the semiconductor industry, and to a process for the ultra-fine pattern formation therewith and, more particularly, relates to a composition for ultra-fine pattern formation which comprises a major amount of an acrylic and/or vinyl ketone polymer and an effective amount of a specified aromatic compound, and a process for ultra-fine pattern formation which comprises coating the composition on a substrate and irradiating with a corpuscular beam or an electromagnetic wave to pattern the resulting film.
2. Description of the Prior Art
The production of electronic devices in the semiconductor industry requires a number of processing steps, including photolithography. The currently used photolithography includes processing by irradiation with ultraviolet light and requires light exposure techniques and a photosensitive material adaptable for processing, that is, a photoresist. In conventional photolithography, a thin layer of a material to be etched, such as silicon oxide, silicon nitride or polysilicon having a thickness on the order of thousands of angstroms is formed on a silicon wafer, a resist film is coated thereon, the resulting film is irradiated with ultraviolet light through a predetermined photomask, and is then subjected to conventional wet development and rinsing. Etching of the silicon oxide layer or the like is effected, the photoresist is removed, the wafer is rinsed well and dried, and an impurity is allowed to diffuse through the exposed area of silicon to be implanted thereinto. Semiconductor devices are manufactured by repeating the above photolithography several times, followed by the preparation of electrodes and wirings.
The conventionally used photoresist in the semiconductor industry includes a negative photoresist which is crosslinked for insolubilization by irradiation with ultraviolet light or the like, and a positive photoresist which is decomposed for dissolution by irradiation. Among the light or corpuscular beam sensitive photoresists, the negative photoresist is such that unexposed areas are selectively dissolved for removal with an organic solvent or an alkali solution, which is termed a "developer", and the positive photoresist is such that exposed areas are selectively dissolved for removal therewith, respectively, to obtain an ultra-fine pattern as required. Examples of the negative photoresist currently used include OMR marketed by Tokyo Ohka Kogyo Co., KMR marketed by Eastman Kodak Co., Waycoat marketed by Hunt Chemical Corp., and the like. Examples of the positive photoresist currently used include OFPR marketed by Tokyo Ohka Kogyo Co., AZ marketed by Shipley Co., KMPR marketed by Eastman Kodak Co., HPR marketed by Hunt Chemical Corp., and the like. An example of an electron beam radiation sensitive resist is OEBR marketed by Tokyo Ohka Kogyo Co. and an example of a deep-ultraviolet light sensitive resist is ODUR marketed by Tokyo Ohka Kogyo Co.
After irradiation with the active light, all of the aforesaid photoresists are subjected to development and rinsing by a wet process using an organic solvent or alkali solution. A resist image thus obtained is used as a mask for etching of the substrate with a fluoric acid (e.g., hydrofluoric acid) etching solution. Dry etching of the surface of a substrate with a plasma prepared from a reactive gas such as CF.sub.4 gas, CF.sub.4 -O.sub.2 mixed gas, CCl.sub.4 gas, CCl.sub.4 -Ar mixed gas, CCl.sub.4 -He mixed gas or the like is becoming widely available. After etching, the resist image is usually removed with a stripping solution of an organic solvent. Ashing for dry removal of the resist, as well as dry cleaning of the substrate by exposing the wafer to an oxygen gas plasma, is known. Development, however, is still being effected according to the conventional wet process described above.
In the conventional wet process of development and rinsing, the organic solvent swelling of the resist and penetrating of the solvent between the resist layer and the substrate are considered to be one of the reasons for reduction in dimensional reproducibility of the resist image, which results in reduction in processing precision, reduction in productivity and the like. The use of such organic solvent and alkali solution is associated with such problems as worsening the working atmosphere, reduction in safety for operators, requirements for the waste liquor treatment, extension of the operating time, complexity and difficulty for automation, development of environmental pollution and the like. Moreover, the worldwide price increase for petroleum resources results in price increase for all kinds of petroleum products, including organic solvents used for conventional lithography. Thus, the use of such solvent presents a serious economic problem.